The present invention relates to processing data or information, and more particularly to storage thereof, when said storage has to be performed with a high degree of security.
In numerous applications, and in particular those related to distributed computing, it is desirable to have stable memories available.
A stable memory is a data storage device which possesses the following properties: firstly, the physical storage of information is stable, i.e. information does not tend to disappear with passage of time; and, secondly, the operation of writing is capable of being made "atomic", i.e. once information has been presented for writing, onc can be certain that the information is correctly written or else it is not written at all.
At present, stable memories are made from disks. Although disks do not directly provide stable data storage, they enable such stable storage to be obtained, in particular by conjoint use of two disk units. However, this method of proceeding has drawbacks. The first drawback is that the access time to a disk memory is not short enough for a stable storage unit based on disks to be considered as being a fast memory. The other drawback is that the stable character of the memory is obtained by copying the same information into both disk units. The controlling processor uses its own read/write memory to perform this double copying operation. As a result, if an error occurs in said processor between writing to one of the disks and writing to the other disk, the stable character of information storage is compromised.